Large-Scale Synthesis and Raman and Photoluminescence Properties of Single Crystalline β-SiC Nanowires Periodically Wrapped by Amorphous SiO2 Nanospheres 2

Novel SiC/SiO2 chainlike nanostructures have been synthesized via a simple template/catalyst-free chemical vapor reaction approach using Si-SiO2 mixture powder and CH4 as raw materials at relatively low temperatures of 1250-1200 degrees C. Digital camera, stereoscope, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and infrared spectroscopy demonstrate that large-scale blue products have been obtained on graphite substrate; the samples are composed of chainlike nanostructures having lengths up to several tens of micrometers, diameters of 20-30 nm single crystalline beta-SiC nanowires, and 80-100 nm amorphous SiO2 Periodic wrapping spheres, possessing [111] preferred growth direction with a high density stacking faults and twin defects. We suppose the formation of the nanostructure is induced by two-stage VS growth mechanism, especially because the defects within SiC nanowires are the critical factors for the second-stage formation Of SiO2 spheres. Some unique optical properties are observed in the room-temperature Raman spectroscopy and photoluminescence measurements of the products, which may be ascribed to crystal defects and size confinement effects.